This invention relates to a method and system for erecting wind energy turbines that allow one to avoid the use of specialized and expensive cranes.
Wind turbines are becoming ever more popular as the expense of electrical energy continues to increase. A typical wind turbine uses a rotary driven generator mounted atop a tower which can reach 80 meters or more in height. The next generation of towers will reach a height of 120 meters at the hub. In fact, 1.5 MW-2.5 W generators at 80 meters high are the staple of this industry because of what the highway systems can operate. The current method to erect towers with 80 meter hub height is with 3 cranes. A 50 ton crane is used for the blades and the hub to suspend them for pre-assembly prior to the use of a 450 ton crane to take the assembly to the 80 meter level. Prior to raising the assembly a 250 ton crane will set the first two tower sections. The first tower section is 90′ long with a 14′ diameter at the base and weighs approximately 90,000 pounds. The next section is 75′ and 75,000 pounds and the section diameter decreases to around 12′. The third tower section and final 75′ section weighs less than 75,000 pounds and tapers to 8′ in diameter. This piece is lifted by the 450 ton crane while the erectors are inside the towers on spiral stairs making connections using the interior flange bolt method, as does all the components above the base. It therefore takes 2 cranes to set the towers upright prior to erection.
Typically the three above-referred to tower sections come to the building site on large trucks, as does the wind turbine housing, hub, and the blades, which themselves are normally 145′ long. The large cranes used in the typical tower erection often are very expensive, renting for $88,000/week or $240,000/month plus maintenance. Furthermore, 38 trucks are required to mobilize the cranes and cost $100,000 to bring into the site as well as out. Thus, time is of the essence and a way to avoid the use of, for example, a 450 ton crane would be hugely desirable and save money.
There have been attempts in the past to eliminate large high tonnage lifting cranes for erecting wind turbines. Those for the most part have been unsuccessful since they themselves are highly specialized and expensive equipment. Such an example is U.S. Pat. No. 6,868,646 which uses a climber device. One problem with such devices is that strength of the structure is not increased as the device climbs the erected tower sections and the first tower section must still be set with a heavy duty crane. Another problem is the expense and slowness of operation. With the enormous forces exerted on the tower that is being climbed in U.S. Pat. No. 6,868,646, it is likely that one would still need a large crane or another device to set the generator and the hub.
Accordingly there is a continuing need for the development of wind energy turbine erection devices which are cheap in construction, which increases in load bearing strength when the wind turbine is being erected, and which avoids the use of highly expensive large tonnage cranes on the job site.
This invention has as its primary objective the fulfillment of this continuing need by developing a new erection system and method which is quick, inexpensive, superior in economics and construction strength (load bearing capacity during erection).
A further object of the present invention is to provide an improved method of attaching a hub with rotor blades to the housing atop the wind turbine tower sections.
These and other objects will be apparent to those skilled in the art.